AGRICULTURAL  EXPERIMENT  STATION 
UNIVERSITY     OF     CALIFORNIA 

BENJ.    IDE    WHEELER,    PRESIDENT 

COLLEGE  OF  AGRICULTURE  thomas  forsyth  hunt,  dean  and  director 


BERKELEY 


E.    VAN    NORMAN,    Vice-Director    and    Dean 
University    Farm    School 


CIRCULAR  No.  111. 

December,  1913. 

THE  USE  OF  LIME  AND   GYPSUM  ON  CALIFORNIA  SOILS. 

By  Ciias.   B.   Lipman. 

Much  confusion  exists  in  the  popular  mind  with  reference  to  the 
actual  nature  of  lime  and  its  use.  The  following  brief  statements  are 
intended  to  clear  up  difficulties  which  exist  and  to  reply  to  frequently 
recurring  questions  on  the  important  subjects  of  lime  and  its  use  and 
gypsum  and  its  use. 

The    Nature   and    Functions   of   Lime. 

The  term  "lime,"  as  we  may  employ  it  in  the  agricultural  sense, 
includes  the  following  materials:  Burnt  lime  (oxide  of  calcium), 
hydrated  or  water-slaked  lime  (hydrate  of  calcium),  ground  limestone 
or  air-slaked  lime  (carbonate  of  calcium).  Even  in  the  agricultural 
sense  the  term,  lime  does  not  include  gypsum.  The  latter  is  an  entirely 
different  substance  from  the  three  named  above,,  as  will  be  explained 
later.  Speaking  with  the  correctness  of  the  chemist  the  term  "lime" 
is  applied  only  to  burnt  lime  (quicklime)  or  calcium  oxide.  Just  how 
the  three  materials  discussed  agriculturally  under  the  name  lime  are 
to  be  employed  and  where  one  is  to  be  preferred  to  the  other,  if  at  all, 
are  questions  which  are  answered  below. 

Before  going  into  a  detailed  description  of  the  mission  or  the  func- 
tion of  lime  in  soils  it  is  well  to  state  clearly  the  relative  values  for 
practice  of  (1)  the  burnt,  caustic,  or  quicklime;  (2)  the  hydrated  or 
water-slaked  lime,  and  (3)  the  carbonate  or  air-slaked  lime.  These 
lime  materials  are  largely  valued  for  the  amount  of  calciuim  oxide  whieli 
they  contain.  Quicklime  is  nearly  all  calcium  oxide.  Hydrated  lime 
or  water-slaked  lime  contains  less  calcium"  oxide  but  may  be  looked  upon 
in  practice  as  nearly  equivalent  ton  for  ton  to  the  quicklime.  Air-slaked 
lime  (like  the  ground  limestone)  or  carbonate  of  lime  contains  only  a 
little  more  than  half  the  amount  of  calcium  oxide  that  the  quicklime  does 
and  therefore  two  tons  of  it  should  be  employed  if  it  is  used  in  place  of 
the  caustic  form.  The  relative  money  values  can  be  determined  at  any 
time  from  the  foregoing  explanation  of  relationship  between  the  differ- 
ent lime  materials.  It  must  also  be  remembered  in  that  connection,  how- 
ever, that  the  cost  of  handling  larger  quantities  and  additional  freight 
rates  involved  must  always  be  taken  into  consideration  in  calculating 
the  actual  and  relative  cost  of  the  different  materials.  The  following 
is  a  consideration  of  the  function  of  lime  materials  in  soils : 

1.  Lime  materials  have  the  power  of  shrinking  clay  and  making  it 
more  pervious  to  water  and  air,  by  making  a  large  number  of  crumbs 
from  large  sticky  masses.  Therefore,  lime  makes  clays  and  clay  adobe 
soils  looser,  prevents  their  packing,  baking  and  cracking,  makes  plowing 


—  2  — 

and  cultivating  easier,  and,  in  general,  makes  the  soil,  physically,  a 
healthier  medium  for  plant  growth. 

2.  Lime  materials  (as  above  described)  serve  as  a  source  of  the 
element  calcium  to  plants.  Calcium  is  one  of  the  ten  essential  chemical 
elements  in  plant  growth. 

3.  Lime  materials  make  "sour"  soils  "sweet."  Speaking  correctly, 
they  change  an  acid  soil  condition  to  a  slightly  alkaline  one.  Acidity 
of  soils  is  very  detrimental  to  the  growth  of  many  agricultural  crops. 
A  slightly  alkaline  condition  is  ideal  for  them. 

4.  Lime  materials  are  necessary  for  useful  and  beneficial  bacteria 
and  other  microorganisms  of  the  soil.  It  furnishes  these  the  element 
calcium,  which  is  as  essential  to  them  as  to  the  higher  plants.  It  pro- 
motes a  slightly  alkaline  condition  which  is  ideal  for  their  development. 
By  its  physical  effects  lime  produces  good  air  and  moisture  conditions 
for  bacteria  as  above  described. 

5.  Lime  materials  promote  the  normal  decay  of  soil  organic  matter 
through  their  effects  on  the  agencies  of  decay  above  described.  The 
normal  decay  of  organic  matter  in  soil  prevents  accumulation  of  poison- 
ous materials  in  soils  which  are  detrimental  to  plant  growth. 

6.  Lime  will  not  neutralize  sodium  carbonate  or  black  alkali. 

The   Nature  and    Function   of  Gypsum. 

Gypsum  is  the  sulfate  of  calcium  and  therefore  is  not  the  same  as 
"lime"  nor  the  same  as  any  of  the  three  forms  of  the  latter  above 
described.  The  only  thing  which  gypsum  has  in  common  with  the  three 
lime  materials  named,  from  the  point  of  view  of  chemical  composition, 
is  that  it,  like  the  others,  contains  the  element  calcium.  Let  us  study 
its  functions  in  soils. 

1.  Gypsum  exerts  a  similar  effect  to  that  of  lime  on  the  clay  and 
adobe  soils   (see  above). 

2.  Gypsum,  like  lime,  serves  as  a  source  of  the  element  calcium  (see 
above ) . 

3.  Gypsum,  like  lime,  stimulates  the  beneficial  soil  organisms  on  the 
roots  of  luguminous  plants  like  the  peas,  beans,  vetches,  alfalfas  and 
clovers. 

4.  Gypsum  does  not  make  "sour"  soil  "sweet."  It  will  not  change 
an  acid  into  a  slightly  alkaline  soil  as  do  the  lime  materials.  Gypsum 
is  a  neutral  salt  (possesses  no  alkalinity) ,  and  therefore  will  not  be  of 
assistance,  or  act  as  a  corrective  to  a  "sour"  or  acid  soil. 

.">.  Gypsum  does  not  share  with  lime,  to  any  appreciable  extent,  the 
good  effects  of  the  latter  on  soil  organic  matter  (see  above). 

6.  Gypsum  will  neutralize  sodium  carbonate  or  "black  alkali." 

Lime  versus  Gypsum. 

The  question  comes  to  us  so  frequently  as  to  whether  "lime  or  gyp- 
sum" will  correct  a  certain  difficulty  in  soils.  This  confusion  of  two 
distinct  types  of  substances  has  done  much  harm,  and  the  reader  is 
asked  to  read  carefully  the  statements  made  above  with  respect  to  each 
in  order  that  errors  may  be  obviated.  As  above  noted  there  are  at  least 
1  wo  very  important  functions  which  lime  performs  in  the  soil  which 
gypsum  can  not  perform.  If  soils  need  correction  for  acidity,  or  it 
is  desired  to  promote  normal  decay  of  organic  matter  only,  the  lime 


materials  will  do  and  not  the  gypsum.  Too  much  emphasis  can  not 
be  placed  on  this  distinction.  In  fact,  to  be  on  the  safe  side  the  use 
of  lime  is  advised  even  in  cases  in  which  people  with  exact  informa- 
tion might,  perhaps,  give  the  preference  to  gypsum.  The  distinct  and 
limited  uses  for  gypsum  are  below  described,  however,  to  serve  as  a 
guide. 

Lime  on    Heavy  Soils. 

No  determination  needs  to  be  made  to  inform  the  owner  of  heavy 
land  if  lime  is  necessary  to  improve  its  texture  as  above  described.  The 
decision  both  as  to  the  amount  to  apply  and  as  to  the  feasibility  of 
applying  it  must  be  made  on  the  basis  of  the  cost  of  lime  and  the  degree 
of  "running  together"  or  baking  and  cracking,  which  is  characteristic 
of  the  soil.  From  one  to  two  tons  of  the  burnt  lime  or  of  the  hydrated 
lime,  or  from  two  to  four  tons  of  the  ground  limestone,  may  be  safely 
applied  to  improve  the  working  qualities  of  heavy  soils.  Application 
may  be  made  by  means  of  one  of  the  several  types  of  lime  spreading 
machines  or  the  lime  may  be  deposited  in  piles  and  spread  with  a  shovel. 
It  should  be  well  plowed  in  and  covered  up  at  a  time  when  there  is 
sufficient  moisture  in  the  soil  for  the  lime  to  act  well. 

The  burnt  lime  or  the  hydrated  lime  is  to  be  preferred  to  the  car- 
bonate of  lime  for  making  heavy  soils  lighter  if  the  cost  will  allow. 
The  first  two  forms  act  more  vigorously  and  more  quickly.  Applica- 
tions of  lime  are  best  made  prior  to  fall  or  winter  plowing  or  several 
months  prior  to  planting.  This  must  particularly  be  borne  in  mind  if 
either  burnt  lime  or  hydrated  lime  are  employed. 

Lime  on   "Sour"  or  Acid   Soils. 

If  "sour"  soils  are  also  heavy  clays  or  clay  adobes,  the  recommenda- 
tions for  the  use  of  lime  above  made  for  heavy  soils  are  to  be  followed. 
If  sour  soils  are  loams,  silts  or  sands,  the  ground  limestone  is  to  be 
preferred  to  the  other  forms  of  lime  where  it  is  obtainable. 

To  test  your  soil  for  sourness  or  acidity  proceed  as  follows :  Mix 
some  of  the  surface  soil  to  be  tested  and  moisten  thoroughly.  Mold  it 
into  a  ball  of  wet  earth  about  three  or  four  inches  in  diameter.  Break 
the  ball  in  two  and  on  one  of  the  broken  surfaces  place  two  strips  of 
red  litmus  paper  previously  moistened  with  clean  boiled  water.  (Lit- 
mus paper,  both  red  and  blue,  may  be  obtained  in  the  drug  stores.) 
Set  the  broken  surfaces  of  earth  together  again  and  press  tightly.  Per- 
form the  same  test  with  another  ball  of  earth,  but  use  blue  instead  of 
red  litmus  paper.  Allow  the  balls  of  earth  to  lie  undisturbed  for  half 
and  hour  •  then  open,  and  if  the  red  litmus  paper  has  turned  blue  no 
lime  is  needed.  If  it  remains  red,  and  the  blue  litmus  paper  turns  red, 
lime  is  needed  and  should  be  applied  as  above  directed.  If  neither  the 
red  nor  the  blue  litmus  paper  should  change  color  during  half  an  hour 
or  more,  then  the  reaction  of  the  soil  is  neutral  and  small  applications 
of  ground  limestone,  not  to  exceed  one  ton  per  acre,  will  be  sufficient. 

When   and    How   Gypsum    May   be   Used. 

Gypsum  may  be  used  to  good  advantage  on  alfalfa  fields  to  stimulate 
the  growth  of  the  plants.  This  is  especially  to  be  remembered  in  con- 
nection with  alfalfa  fields  of  several  years  standing  in  which  bald  spots 


or  bare  patches  are  found.  An  application  of  gypsum  in  such  cases, 
not  to  exceed  300  or  400  pounds  to  the  acre,  along  with  fall  disking 
will  give  striking  stimulation  to  the  plants  and  rejuvenate  the  field. 
The  reason  for  this  is  that  gypsum  is  a  stimulant  to  the  alfalfa  plant 
itself  and  to  the  nitrogen  gathering  bacteria  which  grow  in  the  nodules 
on  its  roots. 

If  lime  is  very  expensive,  as  it  may  be  in  some  districts  of  this  State, 
gypsum,  if  much  cheaper,  may  also  be  used  as  indicated  above,  to  lighten 
heavy  soils.  Applications  varying  from  one  half  ton  to  one  ton  per 
acre  may  be  used  in  such  cases. 

Another  use  for  gypsum,  which  is  more  limited,  consists  in  applying 
it  to  "black  alkali"  land  to  neutralize  or  make  harmless  the  black 
alkali.  In  this  respect  gypsum  can  not  be  replaced  by  lime.  The 
amounts  to  be  used  in  such  cases  will  depend  on  the  amount  of  black 
alkali  present  in  the  soil.  This  must  be  determined  for  those  interested 
by  the  Experiment  Station,  which  should  be  communicated  with  under 
such  circumstances. 


